This invention relates to a method of rock bolting by inserting a rock bolt in a borehole which rock bolt comprises a radially expansible tube which, before being used, has a deep longitudinal depression and is closed at its inner end, and then coupling the outer end of the tube to an external source of hydraulic high pressure fluid so that the tube is plastically deformed to expand so as to cause permanent gripping action, whereafter, the tube is relieved of pressure.
The invention relates also to a rock bolt.
Such a method is described in European patent publication No. EP-A-0016742. The expansible rock bolts described in the mentioned publication have good rock reinforcing properties and their installation is very simple and fast. One size of bolt has a relatively large diameter range and the bolts have been manufactured in more than one size in order to cover almost all drilling equipment.
It is an object of the invention to extend the diameter range of an expansible rock bolt and to improve the anchoring. This is achieved by the definitions of the characterizing part of the claims.